After is defined as both a preposition and a conjunction, as is before.
In a sentence that uses after or before, how can one determine whether it is functioning as a preposition or a conjunction?
Take, for example, these sentences:
- Before/After breakfast, Mac had a headache.
- Before/After eating breakfast, Mac had a headache.
- Before/After he ate breakfast, Mac had a headache.
What is the grammatical function of before/after in each of these sentences? How did you determine whether after/before was a preposition or a conjunction?